Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session L10: Nuclear Structure |
Hide Abstracts |
Sponsoring Units: DNP Chair: Jolie Cizewski, Rutgers Room: Governor's Square 10 |
Sunday, May 3, 2009 3:30PM - 3:42PM |
L10.00001: One-neutron knockout from $^{45}$Cl L.A. Riley, B.A. Hartl, K.E. Hosier, D.C. Stoken, P.D. Cottle, K.W. Kemper, P. Adrich, T.R. Baugher, D. Bazin, J.M. Cook, C. Aa. Diget, A. Gade, D.A. Garland, T. Glasmacher, A. Ratkiewicz, K.P. Siwek, D. Weisshaar Single-neutron structure near the $N=28$ nucleus $^{45}$Cl has been studied via the one-neutron removal reaction $^{9}$Be($^{45}$Cl,$^{44}$Cl)X. Three gamma-rays de-exciting states in $^{44}$Cl have been observed. A proposed level scheme is presented. The angular momentum of the neutron removed has been extracted from measured parallel momentum distributions of the beam-like reaction product. A comparison of measured cross sections with shell-model spectroscopic factors highlights the selectivity of the one-nucleon knockout reaction. [Preview Abstract] |
Sunday, May 3, 2009 3:42PM - 3:54PM |
L10.00002: The third generation $\Lambda$ hypernuclear spectroscopy via the(e, e'K$^+$) reaction at Jefferson Lab Daisuke Kawama Spectroscopic studies of $\Lambda$ hypernuclei via the (e,e'K$^{+}$) reaction play an important role to investigate $\Lambda$ hypernuclear structure. The reaction favorably excites spin-filp states and produces mirror hypernuclei compared to hypernucleus via meson-induced reactions. So far, as a counter experiment, this is the only technique that allows absolute mass determination of hypernuclei with accuracies of a few 100 keV or better. Two previous experiments that we performed, JLab E89-009 and E01-011, established the experimental technique and we obtained hypernuclear mass spectra up to A $\sim$ 30 with energy resolution of $\le$ 400 keV (FWHM). Our next experiment will investigate $\Lambda$ hypernuclei in wide mass region up to A $\sim$ 50. A newly constructed electron spectrometer (HES) and splitter magnet will increase the hypernuclear yield by about 5 times while preserving the achieved energy resoluton. Together with the existing kaon spectrometer (HKS), the installation in Jefferson Lab's Hall C is starting from spring 2009. This presentation will give the latest preparation status of the experiment and outline of the experimental program and technique of the JLab E05-115 experiment. [Preview Abstract] |
Sunday, May 3, 2009 3:54PM - 4:06PM |
L10.00003: Two Proton Knockout from $^{32}$Mg P. Fallon, E. Rodriguez-vieitez, A.O. Macchiavelli, R.M. Clark, I-Y. Lee, M. Wiedeking, A. Gade, P. Adrich, D. Bazin, M. Bowen, C.M. Campbell, J.M. Cook, D.C. Dinca, T. Glasmacher, S. McDaniel, W.F. Mueller, A.F. Ratiewicz, K. Siwek, J.R. Terry, D. Wiesshaar, K. Yoneda, B.A. Brown, T. Otsuka, J.A. Tostevin, Y. Utsuno We present data and calculations on the near-dripline nucleus $^{30}$Ne. Gamma-ray decays from excited states as well as inclusive and exclusive cross-sections were measured in the $^{9}$Be($^{32}$Mg,$^{30}$Ne $\gamma )$X two-proton knockout reaction at incident beam energies of 99.7 and 86.7 MeV/A. The measured inclusive cross section sigma = 0.22(4)mb is suppressed compared to calculation and is indicative of a reduced overlap of initial and final state wavefunctions. We interpret this reduction as a result of large 4p4h intruder components present in $^{30}$Ne, but not $^{32}$Mg. Large 4p4h amplitudes are predicted to generate increased T=1 paring strengths and to help stabilize the heavier fluorine isotopes against neutron decay. A new gamma-ray transition at 1443 keV is assigned to the decay of the 4$^{+}$ state based on the spin dependent sigma for 2 proton knockout from the (d5/2)$^{4}$ configuration. [Preview Abstract] |
Sunday, May 3, 2009 4:06PM - 4:18PM |
L10.00004: Neutron-proton pairing in a single j-shell and the ground state spin A.O. Macchiavelli, P. Fallon, P. Van Isacker Pairing in exotic nuclei is a subject of active research in nuclear physics. Of particular interest is the competition between standard isovector (T=0, J=0$^{+})$ and isoscalar (T=0, J=1$^{+})$ Cooper pairs, expected to occur only near N=Z nuclei. In this work we present the results of the shell model study of a single-j shell with nucleons interacting via a schematic two-body force of the form V$_{JT}$(x) = (1-x)V$\delta _{J1}$ + x V$\delta _{J0}$ that simulates the competition of these two types of pairing with the control parameter x varying from pure isoscalar (x=0) to pure isovector (x=1). We find that for x $\le $ 0.4 the ground state of the many body system with A particles is no longer that with spin 0$^{+}$, but rather one that corresponds to an aligned state of A/2 quasi-deuterons with spin (A/2)* 1$^{+}$ . We can show in the framework of the SO(8) model that this intriguing phenomenon appears as a consequence of the spin-orbit splitting. Since this transition is not seen in nuclei, we can set some limits to the relative strength of these forces. Furthermore, we can speculate about possible implications in atomic fermions traps where, in principle, the control parameter x can be varied. [Preview Abstract] |
Sunday, May 3, 2009 4:18PM - 4:30PM |
L10.00005: Alpha Decay of Proton-Rich $^{112}$Cs and $^{111}$Xe Lucia Cartegni, Chiara Mazzocchi, Robert Grzywacz, Iain Darby, Sean Liddick, Krzysztof Rykaczewski, Jon Batchelder, Laura Bianco, Carrol Bingham, Elton Freeman, Christopher Goodin, Carl Gross, Alessandra Guglielmetti, David Joss, Shaohua Liu, Marco Mazzocco, Stephen Padgett, Robert Page, Mustafa Rajabali, Mauro Romoli, Paul Sapple, James Thomson, Heidi Watkins We have performed an experiment at the Holifield Radioactive Ion Beam Facility (Oak Ridge National Laboratory) in an attempt to detect a weak alpha branch in the decay of proton emitter $^{112}$Cs. The ions produced in the fusion-evaporation reaction $^{58}$Ni($^{58}$Ni,p3n)$^{112}$Cs were separated in the Recoil Mass Spectrometer and implanted in a double sided silicon strip detector. We were able to establish an upper limit on the alpha branching ratio of $^{112}$Cs, and to measure the alpha branching ratio of $^{111}$Xe. This work was supported under US DOE grants DE-AC05-00OR22725, DE-FG02-96ER40983, and in part by the NNSA through DOE Cooperative Agreement DE-FC03-03NA00143, the UNIRIB Consortium and the UK STFC. [Preview Abstract] |
Sunday, May 3, 2009 4:30PM - 4:42PM |
L10.00006: Single-particle structure of $^{133}$Sn explored through the $^{132}$Sn(d,p) reaction in inverse kinematics K.L. Jones, R.L. Kozub, S.D. Pain, A.S. Adekola, D.W. Bardayan, J.C. Blackmon, K.Y. Chae, K.A. Chipps, J.A. Cizewski, L. Erikson, C. Harlin, R. Hatarik, R. Kapler, J.F. Liang, R.J. Livesay, Z. Ma, B.H. Moazen, C.D. Nesaraja, N.P. Patterson, D. Shapira, J.F. Shriner Jr, M.S. Smith, T.P. Swan, J.S. Thomas Many changes have been observed in nuclei as we move away from the valley of stability and it is important, both to nuclear structure physics and to understanding the synthesis of heavy nuclei in the cosmos, to understand how these changes affect single-particle states, especially around doubly-magic nuclei. A (d,p) reaction was performed in inverse kinematics at the HRIBF using a beam of the exotic doubly-magic nucleus $^{132}$Sn. Emergent protons were detected in a large array of silicon detectors, including an early implementation of ORRUBA. A state in $^{133}$Sn at approximately 1400 keV, possibly the missing p$_{1/2}$ single-particle state, has been observed for the first time. Newly extracted angular distributions will be presented in comparison to those from DWBA calculations. [Preview Abstract] |
Sunday, May 3, 2009 4:42PM - 4:54PM |
L10.00007: Multiple Excited Superdeformed Bands in $^{154}$Dy Q.A. Ijaz, W.C. Ma, A.V. Afanasjev, H. Abusara, Y.B. Xu, R.B. Yadav, Y.C. Zhang, M.P. Carpenter, R.V.F. Janssens, T.L. Khoo, T. Lauritsen, D.T. Nisius The $^{154}$Dy nucleus is located near the upper boundary of the region of superdeformation centered around the doubly magic SD nucleus $^{152}$Dy. In order to further explore the limits of this SD island and to understand the evolution of the proton and neutron orbitals at superdeformation, a detailed study of SD structures in $^{154}$Dy has been carried out through the $^{122}$Sn($^{36}$S, 4n) reaction with the use of the Gammasphere detector array. The high statistics data set has allowed the identification of four new excited SD bands, in addition to the previously observed yrast SD band. The intensities of the bands range from $\sim$0.7\% to $\sim$0.05\% relative to the strongest transition in this nucleus. Detailed properties of the bands, including their transition energies, dynamic moments of inertia, decay patterns, as well as the similarities and differences between these new bands and the SD bands in neighboring nuclei, will be presented. The intrinsic configurations of the bands will be discussed based on Cranked Relativistic Mean Field calculations and the effective alignment method. [Preview Abstract] |
Sunday, May 3, 2009 4:54PM - 5:06PM |
L10.00008: Study of $^{155}$\textrm{Gd} by the (p,d$\gamma$) Reaction J.M. Allmond, C.W. Beausang, T.J. Ross, B.K. Darakchieva The structure of the $N=90$ and neighboring nuclei have been of recent interest due to an unusual number of low-lying $0^+$ states and a rapid change from vibrational to rotational character. The single, unpaired neutron in $^{155}$\textrm{Gd} ($N=91$) acts as a probe to the $^{154}$\textrm{Gd} ($N=90$) core. To study this, an experiment was conducted at the 88-Inch Cyclotron at LBNL using the STARS and LiBerACE detector arrays. A 25 MeV proton beam incident onto a $^{156}$\textrm{Gd} target was used to populate states in $^{155}$\textrm{Gd} by the (p,d$\gamma$) reaction. The exit channel of the reaction and the residual excitation energy of the nucleus were tagged by detecting scattered charged particles in a \textrm{Si} telescope array (STARS) while coincident gamma rays were detected using 6 \textrm{Ge} clovers and 1 \textrm{Ge} LEPS detector of the LiBerACE array. Particle-$\gamma$ and particle-$\gamma$-$\gamma$ correlations are used to probe the structure of $^{155}$\textrm{Gd}. Preliminary results are presented. [Preview Abstract] |
Sunday, May 3, 2009 5:06PM - 5:18PM |
L10.00009: Spin measurement and neutron resonance spectroscopy for $^{155}$Gd Bayarbadrakh Baramsai, G.E. Mitchell, A. Chyzh, D. Dashdorj, C. Walker, T.A. Bredeweg, A. Couture, R.C. Haight, M. Jandel, A.L. Keksis, J.M. O'Donnell, R.S. Rundberg, J.M. Wouters, J.L. Ullmann, D.J. Viera, U. Agvaanluvsan, F. Becvar, M. Krticka The $^{155}$Gd(n,${\gamma}$) reaction has been measured with the DANCE calorimeter at Los Alamos Neutron Science Center. The highly segmented calorimeter provided detailed multiplicity distributions of the capture $\gamma$~-~rays. With this information the spins of the neutron capture resonances have been determined. The improved sensitivity of this method allowed the determination of the spins of even weak and unresolved resonances. With these new spin assignments as well as previously determined resonance parameters, level spacings and neutron strength functions are determined separately for s-wave resonances with J = 1 and 2. [Preview Abstract] |
Sunday, May 3, 2009 5:18PM - 5:30PM |
L10.00010: Isomer Spectroscopy of the Heaviest Elements Roderick Clark A new generation of experiments on the structure and properties of the heaviest elements is being performed in laboratories around the world. These studies are addressing fundamental questions such as the maximum mass and charge that a nucleus can attain. Long-lived high-K isomers are found in the region of prolate-deformed trans-fermium nuclei and by studying their decay one can learn about the single-particle structure, pairing correlations, and excitation modes of the heaviest nuclei. Recent decay spectroscopy experiments using the Berkeley Gas-Filled Separator (BGS) at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory have yielded a wealth of detailed new information on many nuclei in the trans-fermium region. I will discuss these new results and their implications. [Preview Abstract] |
Sunday, May 3, 2009 5:30PM - 5:42PM |
L10.00011: Modern Energy Density Functional for Nuclei Shalom Shlomo, David Carson Fuls The development of a modern and more realistic nuclear energy density functional (EDF) for accurate predictions of properties of atomic nuclei is a current subject of enhanced activity. Adopting the standard parametrization of the Skyrme type interactions, we have recently determined within the Hartree-Fock (HF) approximation a new and more realistic EDF by carrying out, using the simulating annealing method (SAM), a fit to an extensive set of experimental data on binding energies, radii, single particle energies and giant resonance energies of nuclei. We also imposed additional constraints, such as the Landau stability constraints on nuclear matter (NM) and the non- negativity of the slope of the symmetry energy density at high density of NM. We have also addressed the issues of the isospin dependence of the spin-orbit (SO) interaction, of the effects of long-range correlations on properties of nuclei and of the equation of state of symmetric and asymmetric NM. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700